Colloid osmotic pressure of interstitial fluid in rat subcutis and skeletal muscle: comparison of various wick sampling techniques

1988 ◽  
Vol 133 (2) ◽  
pp. 167-175 ◽  
Author(s):  
H. WIIG ◽  
S. HEIR ◽  
K. AUKLAND
Keyword(s):  
Skeletal Muscle ◽  
Osmotic Pressure ◽  
Interstitial Fluid ◽  
Colloid Osmotic Pressure ◽  
Sampling Techniques

scholarly journals The Colloid Osmotic Pressure Across the Glycocalyx: Role of Interstitial Fluid Sub-Compartments in Trans-Vascular Fluid Exchange in Skeletal Muscle

2021 ◽  
Vol 9 ◽  
Author(s):  
Fitzroy E. Curry ◽  
C. Charles Michel
Keyword(s):  
Skeletal Muscle ◽  
Steady State ◽  
Osmotic Pressure ◽  
Capillary Pressure ◽  
Interstitial Fluid ◽  
Protein Composition ◽  
Colloid Osmotic Pressure ◽  
Endothelial Glycocalyx ◽  
Fluid Exchange ◽  
Small Pore

The primary purpose of these investigations is to integrate our growing knowledge about the endothelial glycocalyx as a permeability and osmotic barrier into models of trans-vascular fluid exchange in whole organs. We describe changes in the colloid osmotic pressure (COP) difference for plasma proteins across the glycocalyx after an increase or decrease in capillary pressure. The composition of the fluid under the glycocalyx changes in step with capillary pressure whereas the composition of the interstitial fluid takes many hours to adjust to a change in vascular pressure. We use models where the fluid under the glycocalyx mixes with sub-compartments of the interstitial fluid (ISF) whose volumes are defined from the ultrastructure of the inter-endothelial cleft and the histology of the tissue surrounding the capillaries. The initial protein composition in the sub-compartments is that during steady state filtration in the presence of a large pore pathway in parallel with the “small pore” glycocalyx pathway. Changes in the composition depend on the volume of the sub-compartment and the balance of convective and diffusive transport into and out of each sub-compartment. In skeletal muscle the simplest model assumes that the fluid under the glycocalyx mixes directly with a tissue sub-compartment with a volume less than 20% of the total skeletal muscle interstitial fluid volume. The model places limits on trans-vascular flows during transient filtration and reabsorption over periods of 30–60 min. The key assumption in this model is compromised when the resistance to diffusion between the base of the glycocalyx and the tissue sub-compartment accounts for more than 1% of the total resistance to diffusion across the endothelial barrier. It is well established that, in the steady state, there can be no reabsorption in tissue such as skeletal muscle. Our approach extends this idea to demonstrate that transient changes in vascular pressure favoring initial reabsorption from the interstitial fluid of skeletal muscle result in much less fluid exchange than is commonly assumed. Our approach should enable critical evaluations of the empirical models of trans-vascular fluid exchange being used in the clinic that do not account for the hydrostatic and COPs across the glycocalyx.

Transcapillary Starling forces using membrane osmometry

1980 ◽  
Vol 238 (6) ◽  
pp. H886-H888
Author(s):  
J. L. Christian ◽  
R. A. Brace
Keyword(s):  
Osmotic Pressure ◽  
Interstitial Fluid ◽  
Subcutaneous Tissue ◽  
Fluid Pressure ◽  
Colloid Osmotic Pressure ◽  
Interstitial Fluid Pressure ◽  
Tissue Samples ◽  
Small Pore ◽  
The Difference ◽  
Good Agreement

Membrane osmometry was used to estimate the four transcapillary Starling pressures in subcutaneous tissue of rats, guinea pigs, and dogs. Isolated subcutaneous tissue samples were either placed on a large-pore or small-pore osmometer that measured the interstitial fluid pressure (Pif) and the difference between the interstitial fluid pressure and the interstitial protein osmotic pressure (Pif-pi if), respectively. The colloid osmotic pressure of the interstitial fluid (pi if) was obtained from the difference in these two pressures. A plasma sample placed on the small-pore osmometer yielded the colloid osmotic pressure of the plasma proteins (pi c). Finally the capillary pressure (Pc) was calculated from the three other Starling forces. In the rat, guinea pig, and dog, respectively, the estimated Starling forces were as follows: Pif -2.2, -2.1, and -4.8 mmHg; pi if, 7.3, 4.8, and 4.4 mmHg; pi c, 21.3, 19.5, and 19.2 mmHg; and Pc, 11.8, 12.6, and 10.0 mmHg. A comparison with data obtained in other studies using different methods shows good agreement and strongly supports membrane osmometry as a method for measuring the Starling pressures in subcutaneous tissue.

Lowering of interstitial fluid pressure in rat submandibular gland: a novel mechanism in saliva secretion

2006 ◽  
Vol 290 (4) ◽  
pp. H1460-H1468 ◽  
Author(s):  
Ellen Berggreen ◽  
Helge Wiig
Keyword(s):  
Osmotic Pressure ◽  
Submandibular Gland ◽  
Interstitial Fluid ◽  
Fluid Transport ◽  
Fluid Pressure ◽  
Myoepithelial Cells ◽  
Colloid Osmotic Pressure ◽  
Interstitial Fluid Pressure ◽  
High Rate ◽  
Fluid Filtration

The submandibular gland transports fluid at a high rate through the interstitial space during salivation, but the exact level of all forces governing transcapillary fluid transport has not been established. In this study, our aim was to measure the relation between interstitial fluid volume (Vi) and interstitial fluid pressure (Pif) in salivary glands during active secretion and after systemically induced passive changes in gland hydration. We tested whether interstitial fluid could be isolated by tissue centrifugation to enable measurement of interstitial fluid colloid osmotic pressure. During control conditions, Vi averaged 0.23 ml/g wet wt (SD 0.014), with a corresponding mean Pif measured with micropipettes of 3.0 mmHg (SD 1.3). After induction of secretion by pilocarpine, Pif dropped by 3.8 mmHg (SD 1.5) whereas Vi was unchanged. During dehydration and overhydration of up to 20% increase of Vi above control, a linear relation was found between volume and pressure, resulting in a compliance (ΔVi/ΔPif) of 0.012 ml·g wet wt−1·mmHg−1. Interstitial fluid was isolated, and interstitial fluid colloid osmotic pressure averaged 10.4 mmHg (SD 1.2), which is 64% of the corresponding level in plasma. We conclude that Pif drops during secretion and, thereby, increases the net transcapillary pressure gradient, a condition that favors fluid filtration and increases the amount of fluid available for secretion. The reduction in Pif is most likely induced by contraction of myoepithelial cells and suggests an active and new role for these cells in salivary secretion. The relatively low interstitial compliance of the organ will enhance the effect of the myoepithelial cells on Pif during reduced Vi.

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